| Split Thumb | |
| Elevation Ft: | 5523 |
| Elevation Ref: | [1] |
| Prominence Ft: | 923 |
| Isolation Mi: | 2.15 |
| Range: | Coast Mountains Boundary Ranges Juneau Icefield |
| Parent Peak: | Mount Wrather[2] |
| Country: | United States |
| State: | Alaska |
| Region: | Juneau |
| Region Type: | Borough |
| Part Type: | Protected area |
| Part: | Tongass National Forest |
| Map: | USA Alaska |
| Label Position: | left |
| Mapframe: | yes |
| Mapframe-Zoom: | 8 |
| Mapframe-Caption: | Interactive map of Split Thumb |
| Coordinates: | 58.4064°N -134.3122°W |
| Topo: | USGS Juneau B-1 |
| Age: | Late Cretaceous |
| Rock: | Granitic |
| Volcanic Arc/Belt: | Coast Range Arc |
| First Ascent: | July 2, 1954 |
| Easiest Route: | Southeast arête[3] |
Split Thumb is a 5523feet glaciated mountain summit located in the Boundary Ranges of the Coast Mountains, in the U.S. state of Alaska.[4] The peak is situated near the southern periphery of the Juneau Icefield, 90NaN0 northeast of Juneau, 2.15 mi (3 km) southeast of Nugget Mountain, and 40NaN0 east of Heintzleman Ridge, on land managed by Tongass National Forest. Split Thumb is surrounded by the Lemon Creek Glacier to the west, and Norris Glacier to east. The Split Thumb Icefall is set on the east aspect of the peak.[5] This peak's descriptive name was published in 1951 by the U.S. Geological Survey.[4] The first ascent of Split Thumb was made July 2, 1954, by a Juneau Icefield Research Project party comprising Edward LaChapelle, Dick Hubley, Carlton Ray, Dr. Conrad Buettner, and Bob Goodwin.[6]
Based on the Köppen climate classification, Split Thumb is located in a subarctic climate zone, with long, cold, snowy winters, and cool summers.[7] Weather systems coming off the Gulf of Alaska are forced upwards by the Coast Mountains (orographic lift), causing heavy precipitation in the form of rainfall and snowfall. Winter temperatures can drop below 0 °F with wind chill factors below −10 °F. The month of July offers the most favorable weather to view or climb Split Thumb.